Presuming you don't care about what is on the stick now (if you do then use anything you can to access it and get the stuff off it) then just wipe the start of the stick and start again. A command like:

Code:

dd if=/dev/zero of=/dev/sdX bs=1M count=1

should do it (replace /dev/sdX with the device name for your usb stick, above you have /dev/sdb but you should check using dmesg or some other method this is still correct before blindly trying it).